Enzymes are usually provided as liquids or amorphous materials for industrial purposes. When not provided as liquids, they are usually provided as amorphous materials, because the known methods for crystallization of enzymes are usually regarded as too expensive to be used in an industrial scale.
There is an abundance of literature concerning crystallization of enzymes. It is difficult to generalize in respect to the outcome of specific crystallization procedures, as the art of enzyme crystallization is highly empirical.
Characteristic features of most of the hitherto known protein crystallization processes are: Pure and concentrated initial solutions, very long crystallization time, high consumption of chemicals such as salts, for reference see, e.g., Biotechnology and Bioengineering 48, 1995, p. 316-323.
Industrial enzyme crystallization processes using polyethylene glycol have also been described, for reference see WO 95/01989.
It has also been described that it is possible to crystallize enzymes by leaching out salts from the solution, followed by adjustment of the pH of the solution to a level around the pI of the enzyme, for reference see WO 94/22903.